A thermal transfer film includes a light-to-heat conversion (LTHC) layer. The light-to-heat conversion layer absorbs light in a certain wavelength range and converts at least some of the absorbed light into heat. For light-induced thermal transfer, it is desirable that the light-to-heat conversion layer maintain a uniform surface without reducing optical density.
The thermal transfer film further includes a base film which transfers incident laser light to the light-to-heat conversion layer. However, most base films include foreign matters therein. The foreign matters disturb an optical path of the laser light, thereby obstructing transfer of the laser light to the light-to-heat conversion layer and causing transfer failure.
FIG. 5 is a cross-sectional view of a thermal transfer film which includes a base film 10, a light-to-heat conversion layer 20, an interlayer 30, and a transfer layer 40. Foreign matter 50 in the base film 10 can disturb suitable delivery of the laser light to the light-to-heat conversion layer 20. As a result, transfer failure can occur.
In this regard, Korean Patent Registration No. 10-0654649 discloses a thermal transfer element that comprises a transfer layer containing multiple components constructed and arranged to emit or produce light.
Considering a recent trend of providing finer patterns, there is a need for a thermal transfer film capable of preventing transfer failure caused by foreign matter in a base film.